In recent years, electrostatic capacitance type touch panels are used as displays in various devices led by mobile equipment.
As principal ingredients of optical pressure-sensitive adhesives or optical adhesives employed upon assembling individual members that make up such devices, acrylic materials are generally used (see Patent Documents 1 and 2). These acrylic materials have high transparency, but differences arise between their refractive indices and those of the associated surfaces of the individual members, resulting in a problem that light is reflected at the interfaces and the light extraction efficiency is hence lowered.
In view of this problem, technologies have been reported to improve the visibility and light extraction efficiency of an optical member by controlling the refractive index of a multilayered film of the optical member though the use of a composition, which contains a triazine ring-containing polymer and a particular organic solvent, as a refractive index control material for an optical adhesive or a pressure-sensitive optical adhesive (see Patent Document 3).
Nonetheless, due to the inclusion of the organic solvent in the refractive index control material of Patent Document 3, a heating and drying step is needed, and moreover, an adhered member may be deteriorated at a surface thereof with the solvent upon its adhesion.